app/testpmd: remove duplicated flow type name table

app/testpmd: remove duplicated flow type name table

Flow type table has two instance, one is used for flow type to string
conversion, and other is used for string to flow type conversion.
And tables are diverged by time.

Unifying tables to prevent maintaining two different tables.

Note: made 'flowtype_to_str()' and 'str_to_flowtype()' non-static to
prevent build error for the case PMDs using it disables. Making the two
functions generic, not for some PMDs.

Signed-off-by: Ferruh Yigit <ferruh.yigit@xilinx.com>
Signed-off-by: Huisong Li <lihuisong@huawei.com>